Furnace control



Oct. 21, 1924.

E. M LEAN FURNACE CONTROL Filed Aug. 4, 1923 2 Sheets-Sheet l i INVENTOR.

' '11 TTORNEYS Oct. 21, 1924- 1,512,121

E. McLEAN FURNACE CONTROL Filed Aug. 4, 1923 2 Sheets-Sheet 2 -%LJ97Z.

1 N VEN TOR.

v' ATTORNEYS Patented Oct. 21, 1924.

UNITED STATES PATENT OFFICE.

EMBURY MQLEAN, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE ENGINEER COM- PANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

FURNACE CONTROL.

Application filed August 4, 1923.

T all whom it may concern:

Be it known that I, EMBURY MQLEAN, a citizen of the United States, residing in New York city, borough of Brooklyn, county of Kings, and State of New York, have invented certain new and useful Improvements in Furnace Controls, of which the following is a specification.

My invention more particularly relates to a novel method and apparatus for controlling a furnace in which the rate of feed of fuel to the furnace is controlled by the rate of flow of gases through the furnace.

My invention will best be understood by reference to the accompanying drawings which illustrate the preferred form of apparatus for carrying out my invention and in which Figure 1 is a diagrammatic side view of a steam boiler and its furnace with the associated parts, embodying my invention; Fig. 2 is a side view partially in section of the control device for controlling the supply of energy to the motor which operates the stoker, and Fig. 3 is a sectional view through the pilot valve of Fig. 2.

Like reference characters indicate like parts throughout the drawings.

Referring now to the drawings, is a steam boiler heated by a furnace" 11 pro vided with a stoker 12 which is here shown as of the underfeed type. The stoker is operated by a motor here shown as a steam engine 13, the crank shaft 14 of which is provided with a sprocket wheel 15 driving a sprocket wheel 16 on the stoker by means of a sprocket chain 17. The outlet flue for the boiler indicated at 18 is controlled by a plate damper 19 pivoted at 20, said plate damper being movable in order to vary the outlet area of the flue. Mounted on the pivot of the damper is a lever 21 connected by a' flexible member, such as a chain, 22 with a piston rod 23, the lower end of which is attached to a piston 24 in an. operating cylinder 25, which cylinder is adapted to receive a fluid for moving and controlling the piston to vary the position of the damper in the outlet flue. The upper end of the cylinder 25 is connected by a pipe 26 with a source of fluid under pressure, such as water pressure, and represented by the pipe 27, so that the upper end of the cylinder 25 is preferably in permanent com- Serial N0. 655,570.

munication with the source of fluid pressure. The pipe 27 is connected to a port 28 opening into a pilot valve chamber 29, said chamber being also connected by'a port 30 with a pipe 31 leading to the lower end of the cylinder 25. Leading from the pilot valve chamber 29 is a vent 32. Within the chamber 28 is a pilot valve 33 connected at its upper end by a rod 34 to an arm rig-idly mounted on a regulator plate 35 which is or may be mounted and operated similar to the regulator plate shown in my Patent No. 1,355,157 which issued October 12, 1920, and to which reference may be made for fuller details regarding the construction and operation thereof. The pilot valve 33 is so connected to the plate 35 that when the latter is moved by a preponderance of atmospheric pressure over furnace pressure, said valve will uncover the port leading to the vent pipe 32, permitting the fluid in the cylinder 25 beneath the piston 24 to flow out of the cylinder, and as the upper end of the cylinder is permanently connected to the sourcecf fluid pressure, the piston is moved downwardly to cause the plate damper19 to be swung on its pivot to approximately the horizontal position and reduce the outlet area of the flue. When the regulator plate is moved by a preponderance of the furnace gas pressure in excess of the atmospheric pressure, the pilot valve is moved downwardly to a position to cut off communication between the vent pipe 32 and the chamber 28 and to establish communication between said port 30 and the supply pipe 27, whereby the fluid withdrawn is permitted to flow through the pilot valve chamber and the pipe 31 to cylinder 25 beneath the piston 24. In view of the fact that the exposed area on the underside of the piston 24 is greater than the exposed area on the upper side thereof, said piston will be moved upwardly to permit the weight 36, attached to the arm 21 on the plate damper pivot 20, to swing the plate damper to a position to enlarge the outlet area of the flue. The regulator plate 35 with the associated parts, includingthe flue damper, act therefore to maintain substantially uniform pressure of the furnace gases at thepoint of their flow at which the plate regulator 35 is located. The steam engine 13 for operating the stoker is supplied with steam from a steam supply pipe 37 which may be connected to the steam boiler and which conimunicates with the steam engine by a branch pipe 38 in which is located a valve 39 for controlling the steam supply to the engine. The steam supply pipe 37 is also preferably connected to a steam engine 40 which operates a blower 41 for supplying air under forced draft through a passage 42 to the stoker. The steam supplied to the engine for operating the blower may be controlled by a valve 43 which may be controlled in anv desired manner, either manually or automatically.

In accordance with my invention the device for controlling the supply of energy to the motor which actuates the stoker, and.

which is here illustrated as a valve controlling the supply of steam to the steam engine for operating the stoker, is controlled in accordance with the rate of flow of gases through the furnace, and by a device which I have indicated generally at A. The device is mounted on a base or frame 44 as best shown in Figure 2, one end of the frame being provided with an upwardly extending plate 45 provided with an opening 46, a flexible diaphragm 47 being clamped at its edges between the plate 45 surrounding the opening 46 and a casing head 48. A dome or casing 49 is provided at its edges with a flange 50 having a surface adapted to form an air-tight joint with the wall of the plate 45 surrounding the opening 46, the dome 49 with the diaphragm 47 forming a chamber 51 which communicates through a pipe 52 with a point in the flow of gases remote from the point at which the pressure plate 35 is located, and preferably adjacent to the outlet flue 18, so that one side of the diaphragm 47 issubjected to the gas pressure obtaining at the point of the flow ofgases with which the end of the pipe 52 communicates. The movement of the diaphragm 47 is preferably resisted by a constant force, for example, a spring. For this purpose, a stem or rod 53 is attached at its inner end to the diaphragm 47 as by a nut 54, the stem passing through an opening 55 in the casing head 48. A spring 56 is connected at one of its ends to the outer end of the stem53, and its opposite end is secured to an adjustable member 57 secured in a bracket 58 so that an adjustment of the spring 56 may be secured.

In the form shown the valve 39, control ling the supply of steam to the steam engine 13, is operated by a piston 59 in a cylinder 60, the piston being connected by a piston rod 61 to a chain 62 or other flexible connection passing over pulleys 63, 64 and 65 and preferably wound over an operating cam member '66, the free end of the chain being provided with a weight 67. The piston 59 is operated by fluid under pressure from a suitable source represented by the pipe 68 which may be connected to water under pressure. The control of the fluid under pressure to the cylinder 60 is preferably under the control of a valve indicated generally at 69 comprising a cylinder 70, to the middle portion of which the fluid pressure supply pipe 68 is connected. The cylinder 70 is provided at its lower end" with a vent pipe 7 0 and is connected near one end by a pipe 71 to one end of the cylinder 60 and is connected near its other end by a pipe 72 to the opposite end of the cylinder 60. Within the cylinder 70 are two valve heads 73 and 74 connected together by a stem 75 and which normally cover the ports in the cylinder 70 to which the pipes 71 and 72 are respectively connected. The stem'7 5 is connected to the valve heads 73 and 74 and passes through an opening 76 in one end 77 of the cylinder, and is pivoted at its upper end, as at 78, to an intermediate point of a floating lever 79, one end of which is pivoted, as at 80, to a link member 81, the opposite end of the link member being pivoted as at 82, to a bell crank 83, which is pivoted at 84 on a bracket 85 which may be secured to the casing head 48, as illustrated. The opposite end 86 of said bell crank is pivoted, as at 87, to the outer end of the stem 53 heretofore described. The right hand end of the lever 79 is pivoted, as at 88, to the upper end of a stem 89 passing through a stationary sleeve 90, the lower end of the stem 89, which extends below the sleeve 90, preferably being provided with a collar.91 between which and the lower end of the sleeve 90 is interposed a compression spring 92. The lower end of the stem 89 is also provided with a stirrup 93 carrying a roller 94 which engages a cam guide 95 mounted on and movable with a guide rod 96 passing through an opening 97 in the end plate 45 and through openings 98 and 99 in standards 100 and 101 secured to the base or frame 44. The right hand end of the guide rod 96 is ,attached at 102 to the piston rod 61 so that the movement of the piston and its piston rods are communicated to the cam guide 95. The cam 95 is formed on such a curve that when the same is moved to the right or left, the movement communicated to the stem 89, which is moved thereby will be as the square of the movement ofthe piston 59 for a purpose which will presently appear.

Now, when an excess of pressure in the outlet flue over the normal pressure therein occurs, the diaphragm 47 is moved to the right, as viewed in Figure 2, the bell crank 51 is rotated anti-clockwise, the left hand.

end of the lever 79 is lifted around pivot 88, which is now stationary, thereby lifting the valve heads 73 and 74 and opening communication between the fluid pressure pipe 68 and the pipe 71, which leads to the left hand end of the cylinder 60. At the same be moved to the right, thereby lifting the rod 89, rotating the arm 79 about the pivot 80, thereby restoring the valve heads 73 and 74 to their original positions, thereby agaln closing the ports to the pipes 71 and 72.

As the pressure of gases in the gas passage in the boiler will vary as the square of the velocity of the gases through the boiler, it follows that the velocity of flow through the boiler varies as the square root of the variations in pressure of the gases at the diaphragm regulator. Therefore the curve of the cam guide 95 is made such that the rate of feed of fuel will vary directly with the rate of flow of gases through the boiler which is the result desired. The rate of flow of gases through the furnace, or the volume per unit of same, varies as the square root of the difference in pressure between any two points and specifically between the point of uniform pressure and the outlet of the flue; conversely, the difference in pressure between the two said points varies as the square of the rate of flow of gases. Inasmuch as the movement of the diaphragm 47 is in accbrdance with the difference in pressure between the point of uniform pressure of the gases, namely, the point at which the pressure plate 35 is located, and the outlet flue for the gases, with which the pipe 52 communicates, the movement of the piston 59, and, correspondingly the movement of the valve 39, is in accordance with the rate of flow of gases through the furnace. Preferably, the cam member 66 is formed of suitable discs secured together (only one of which is shown in Figure 2), and provided with radial slots 103 in which are secured a series of bolts 104 progressively removed from the center of the cam, as indicated, to form a spiral. .The arm 105, which operates the valve 39, rests upon the uppermost of the bolts 104, the arm 105 being held in engagement with said bolts by counterweight 106. The construction of said cam member is or may be the same as the cam member more fully illustrated in my patent No. 1,355,157 to which reference may be made for fuller details. It will be understood that the bolts 104 in the cam'66 may be various arranged in order to cause a given difference in pressure of the gases to cause any desired amount of steam to flow to the steam engine, and thereby adjust the rate of feed of fuel to anydesired rate of flow of gases.

I claim:

1. The method of operating a furnace which consists in maintaining the furnace pressure substantially uniform at one point in the flow of the furnace gases and utilizing variations in pressure at another point in the flow of furnace, gases for controlling the rate of feed of fuel.

2. The method of operating a furnace which consists in maintaining substantially uniform pressure of the gases at one point in the furnace and regulating the rate of feed of fuel to the furnace in accordance with variations in gas pressure at another point in the flow of gases.

3; In combination, a furnace, means for feeding fuel thereto, means for maintaining at one point in the flow of furnace gases substantially uniform gas pressure, and means responsive to variations in pressure at another point in the flow of gases for varying the rate of fuel feed to the furnace.

4:. In combination, a furnace, means for feeding fuel thereto, means for maintaining at one point in the flow of furnace gases substantially uniform gas pressure, a pressure operated device for controlling the rate of feed of fuel to the furnace and comprising a movable member operable by variations in pressure at another point in the flow of gases, the movement of said movable member being resisted by a constant force.

5. In combination, a furnace, means for feeding fuel thereto, means for maintaining at one point in the flow of furnace gases substantially uniform gas pressure, a movable member operable in accordance with variations in pressure at another point in the flow of gases, and means operable in response to the movement of said movable member for controlling the rate of feed of fuel to the furnace.

6. In combination, a furnace, means for feeding fuel thereto, means for maintaining at one point in the flow of furnace gases substantially uniform gas pressure, a movable member operable in accordance with variations in pressure at another point in the flow of gases, a fluid pressure operated device for controlling the rate of feed of fuel to the furnace, a pilot valve operated in response to the movement of said movable member for controlling the supply of fluid under pressure to said fluid pressure oper-- ated device, and means operated in response to the movement of said fluid pressure operated device for returning said pilot valve to normal position.

7. In combination, a furnace, feeding fuel thereto, means for maintaining at one oint in the flow of furnace gases substantlally uniform gas pressure, a movameans for ble member operable-in accordance with variations in pressure at another point in the flow of gases, :1 fluid pressure operated device for controlling the rate of feed of fuel to the furnace, a pilot valve operated in response to the movement of said movable member for controlling the supply of fluid under pressure to said fluid pressure operated device, and means movable substantially as the square of the movement of said fluid pressure operated device for returning said pilot valve to normal position.

EMBURY MoLEAN. 

